1. Field of the Invention
The present invention relates to a method and device for feeding a recording sheet at a certain speed without variation in feeding speed of the recording sheet, which is occurred in transferring the recording sheet from feeding means to another one.
2. Background Arts
In a printer processor, for instance, recording light beams are projected onto a sheet-type photosensitive recording material (hereinafter referred to xe2x80x9crecording sheetxe2x80x9d) in a main scan direction while the recording sheet is fed in a sub-scan direction perpendicular to the main scan direction, to record an image onto the recording sheet. Along a passage of the recording sheet are provided a plurality of feeding roller pairs, each of which transfers the recording sheet to the next one. The feeding roller pairs are controlled to be equal in the feeding speed.
In order to improve the image quality, it is needed to apply the recording light beams onto the recording sheet with high precision. The recording light beams can be projected in the main scan direction with high accuracy by controlling an optical system in an exposure unit. With regard to the sub-scan direction, the feeding roller pairs provided near an exposure position are designed to feed the recording sheet with high accuracy. However, other feeding roller pairs to provided at upstream and downstream positions of the exposure position are not able to feed the recording sheet with high accuracy. Under the influence of the upstream and downstream feeding roller pairs, the feeding speed of the recording sheet is changed. Thereby, density unevenness in a print picture could be occurred.
In view of the foregoing, an object of the present invention is to provide a method and device for feeding a recording sheet capable of preventing deviation in feeding speed of the recording sheet.
To achieve the above objects, a method for feeding a recording sheet includes the following steps: feeding the recording sheet at a speed V1 by use of first feeding means, transferring the recording sheet to second feeding means from the first feeding means, transferring the recording sheet to third feeding means from the second feeding means, and feeding the recording sheet at a speed V3 by use of the third feeding means. The feeding speed V2 of the second feeding means is set, to be faster than a maximum feeding speed of the first feeding means, and slower than a minimum feeding speed of the third feeding means.
In the preferred embodiment, the first feeding means includes at least one transfer roller pair including a one-way clutch. The second feeding means includes first and second feeding roller pairs arranged sequentially along a feeding passage. The first and second feeding roller pairs rotates at a same speed by a steel belt stretched therebetween. The third feeding means includes a belt conveyor to feed the exposed recording sheet toward a processor section. When the recording sheet is nipped by the first feeding roller pair, the one-way clutch is actuated to make said transfer roller pair free. Moreover, before the trailing end of the recording sheet passes the second feeding roller pair, the recording sheet is fed with the leading end portion thereof being slipped on the belt conveyor.
According to the present invention, since the recording sheet is conveyed at the same feeding speed V2 during transfer, it is possible to prevent deviation in feeding speed of the recording sheet. Thus, image quality of a print image could be improved.